Marchetti’s Wall or Constant

The media have recently picked up on the idea of the “Marchetti Wall” – the idea that, on average, most people spend around 60 to 90 minutes per day travelling, regardless of whether they live in villages, towns or cities. The paper below summarises the concept succinctly.

Of course, the distance travelled will change with technology and improvements to transport networks. However, according to the theory, there is something deeply significant about the 60-90 minutes per day, relating to our most basic human instincts.

This idea is being seized upon by academics and lobbyists, who believe that investments in large infrastructure projects are not the solution to our transport problems. The argument runs that any such investment is counter-productive. Time saved by easing congestion on the roads or public transport will be used to travel more and/or further.

This is actually not such a new idea. The work of Yacov Zahavi in the 1960’s and 1970’s developed the idea of constant ‘travel time budgets’. However, there are variations in travel budgets across different social/income groups which are worth noting. Zahavi spent many years researching these ideas and his views changed over time as the research evolved. The TRL carried out extensive reviews of his work and models which are worth re-visiting. There is a risk of over-simplifying these concepts and they deserve serious thought.

Some of Zahavi’s papers can be found at the site shown below:

On Thursday 2 June 2011, an article by Nicholas Cecil was published in the Evening Standard entitled “Fifth of London commuters take over an hour to get to work”. Cecil states that nearly half of all London employees take over 45 minutes to get to work, and 21% of those with jobs in Inner London take more than an hour. For the UK as a whole about 5% of commuters take an hour or more to get to work. These figures are, presumably, reputable since they were produced by the Office for National Statistics. They represent the situation in 2009.

The London evidence suggests that there are probably significant variations around the averages that Marchetti and Zahavi talk about. It would be interesting to see some in-depth analysis of the relationships between long-commuting journeys and income levels and/or household structures.

As far as I am aware, the work of Marchetti and Zahavi has little to say about travel in the course of business and the transport of goods. Commuting and travel in non-work time, whilst important, are only part of the picture.

In short, I believe that this is an interesting area of research, but over-simplifying the concepts is unhelpful. A truly objective review of the evidence is probably over-due.

Note: minor corrections and modifications to this paper were made on 27/4/2012.

About djtplan

Independent Transport Planner
This entry was posted in Transport Modelling, Transport Planning. Bookmark the permalink.

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